#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    int l=1;
    int r=1e9;
    while (r-l>1) {
        int m=(l+r)/2;
        cout<<"? "<<m<<endl;
        int b;
        cin>>b;
        if (b) l=m;
        else r=m;
    }
    cout<<"! "<<l<<endl;
}